Numerous implantable medical devices (IMDs) are available for acute or chronic implantation within patients. Some implantable medical devices may be used to monitor physiological signals of the patient, such as cardiac pacemakers, implantable hemodynamic monitors, implantable cardiac monitors (sometimes referred to as implantable loop recorders or ECG monitors), implantable blood chemistry monitors, implantable pressure monitors, etc. Among the various types of physiological sensors utilized by medical devices for monitoring patients are electrodes for measuring electrical signals and/or impedances, piezoelectric crystals, accelerometers, pressure sensors, pH sensors, acoustical sensors, temperature sensors, and oxygen sensors.
The physiological signals may be stored, processed and analyzed by the medical device to generate physiological data about a patient useful to a clinician in diagnosing a condition or planning medical treatment. Some implantable devices may be configured to deliver a therapy in conjunction with monitoring of physiological signals. Physiological signals may be processed and analyzed to determine when a therapy is needed or how a therapy needs to be adjusted to benefit the patient. Therapies delivered by an implantable medical device can include electrical stimulation therapies, e.g., cardiac pacing, cardioversion/defibrillation shock pulses, or neurostimulation, and pharmacological or biological fluid delivery therapies.
In order to provide the physiological data needed for detecting pathological conditions, controlling automatic therapy delivery or generating data in a form useful to a clinician for diagnosis and prognosis, an analog signal produced by a physiological sensor often needs to be digitized. An analog-to-digital (A/D) converter is used to convert the analog signal to a digital signal according to a desired sampling rate and bit resolution. When physiological signals are monitored continuously or on a frequent basis, A/D converters included in an IMD can contribute significantly to the overall device power consumption.
An ongoing design goal in medical device technology is device size reduction, e.g. to enable minimally invasive implant procedures and to promote patient comfort. Reduction of device size, however, poses limitations on the space available for power supplies, signal processing circuitry, and other device components that support the primary device function. Systems and methods that reduce the power consumption required by signal processing circuitry, such as A/D converters, can improve the battery longevity of implantable devices and/or contribute to an overall size reduction.